1. Field of the Invention
The present invention relates to implants and prosthesis generally employed in the medical field for repairing or recovering body pieces such as bone pieces, dental pieces, and the like, and more particularly the invention refers to a dental implant, preferably a threaded dental implant, provided with enhanced and improved cutting means at a root of the implant, preferably at a distal end of the implant.
While the present specification makes reference to dental implants as preferred embodiments of the invention it must be clear that the teachings of the invention may be applied to any implant or prosthesis that is to be installed into a bone.
2. Description of the Prior Art
Prosthesis and implants are well known in the medical field; they are employed in connecting broken bones and replacing lost body pieces. More precisely, in the odontology field, dental implants are being more and more employed to replace lost dental pieces, with the implants comprising basically an implant body that is fixed into the maxillary bone by screwing-in or nailing the implant into a bone hole such as the drilled bore or recent post extraction socket in the bone of a patient. Several techniques may be employed to permit correct osseous integration of the implant body into the bone and to wait for healing of the bone and gum. After the healing and integration period an abutment may be fixed into the implant body and a dental prosthesis or crown may be finally mounted and fixed, by screws or cement, onto the abutment and implant body. In some implantation techniques no healing period is waited for and the dental prosthesis and abutment are mounted and fixed to the implant body immediately after the same has been inserted and fixed into the bone.
In any of the techniques presently in practice always the implant must be firmly anchored into the bone in order to prevent undesired movements thereof during healing or after healing. Another problem or difficulty is that when the implant must be installed into the bone bore the length of the implant must be in agreement to the depth of the bore or socket. Preferably, the implant should have exactly the same depth of the bore in order to be firmly retained and anchored against the bottom of the bore. However, this is not an easy task. While the implantologist may take exact measures of the bore depth and the implant length in order to have the bore drilled with the appropriate depth, the irregularities of the bore walls and bottom cause the implant to be usually stagnated into the bore before reaching the bottom as recommended or it contacts the bottom of the bore before reaching the necessary implant-bone interference to be anchored against the bore walls.
If the implant is screwed into the bone and it results stagnated or -firmly anchored against the lateral walls of the bore without reaching and contacting the bottom of the bore, the implant would result in an improper installation with the future disassembling consequences. However, while the implantologist or dentist becomes aware of the misfit and deficient installation generally he/she are not able to remove the implant as long as it has already been firmly wedged into the bore and, if stronger forces are applied onto the implant to remove it from the bore it is quite frequent that the implant body is broken with a part thereof remaining into the bore and with the drastic consequences this may imply.
The reasons of the above difficulties are, among others, the matching complex shapes and materials involved in the attachment as well as the plasticity of the jawbone which is capable of capturing the metallic implant into a firm stagnated position before reaching the bottom of the socket. These difficulties increase as long as the outer surfaces of the implants are provided with means for enhancing osseous integration such as outer surface textures, pores, etc. which causes a problem in the displacement of the implant. When the smooth rounded end of the implant body does not contact the bottom of the socket the threads at the upper or proximal portion of the body do not get enough anchoring against the socket walls. This also prevents the desired helical implant advance, some times, at the beginning of the insertion process.
While an oversized hole depth of about 2 mm serves to more easily position a tapered implant at the correct proximal level this can not be carried out when the patient has a reduced bone height. In addition, a tapered screw can be inserted more easily into a cylindrical drilled bone bore but in detriment of a strong initial stability.
There are a variety of implant systems employing enhanced cutting means at the distal ends thereof to help cutting the bore walls while the implant is being screwed into the bone. An implant of this type is disclosed in U.S. Patent Application published under No. U.S. 2005/0019731 A1 to Bjorn et al. wherein the implant is a self-tapping one including one or more bone-chip recesses for accommodating bone material cut-off during the tapping operation. While the cutting edges defined by the recesses and the threads operate well to cut off the bone, the bottom of the implant is blunt and flat enough to abut against the bottom of the bone socket in a manner to prevent the implant from entering deeper into the socket as long as the cutting off action is exerted only against the vertical walls of the socket.
Other implants having similar cutting recesses are disclosed in published U.S. 2005/0147943 A1; U.S. 2004/0072128 A1; U.S. Pat. No. 5,897,319 and U.S. Pat. No. 6,382,976 B1, all having blunt bottoms or ends that prevent the correct deep cutting off to enter the bone mass. While other implants like the one of U.S. Pat. No. 4,407,620 are provided with sharper ends and cutting edges, the entire implant body rotates in the central point of the bottom tip without permitting to carry out an effective cutting effect and, as an opposite effect, the tip is frequently wedged into the bone mass of the socket bottom preventing the cutting edges from properly cutting off the socket vertical walls. In other words, the central bottom tip operates as a pivot point barring any cutting capacity of the implant.
While the use of cutting grooves for dental implants has been widely extended there are circumstances where the use thereof leads to inconvenient results. As a result of the drilling or cutting action of the grooves the sticky bone material collected into the grooves may cause the implant to be prematurely stacked into the socket. For solving this question the grooves have been made to extend all along the entire length of the implant body with the risk that the body may fracture due to the diminished resistant section of the implant.
According to a well known theory, the hydraulic pressure exerted within the isolated distal space, without immediate drainage, indirectly affects the desired results. To permit the escape of hydraulic pressure, caused by the blood and the grafting material, during the insertion procedure, two or more parallel grooves have been provided. Differing from the well known shorter cutting grooves, these larger grooves extend all along the length of the implant body.
The inventor has found that all of the above improvements in dental implants, while working acceptably, had not provided a final and integral solution to the above disclosed problems of mismatching and lack of firm installation of the implant body into the bone socket.
It would be therefore convenient to have an implant with improved cutting and pressure relief means at the root or distal end of the implant to guarantee a firm and proper installation of the implant into the bone socket.